Central Kentucky Pastures Deemed 'Safe' For Mares

Dr. David Powell of the Gluck Equine Research Center said at the Keeneland informational meeting on the evening of May 24 that he is "confident at this stage that the incidence of problems has dropped significantly." Therefore, he offered the following conclusions:

1--There is no need to ship mares out of Kentucky at this time;

2--Re-establish mares on pastures, except under black cherry trees, since the insult that caused the problems has passed;

3--There will be an emphasis on identifying the cause of the problem, which remains the number one priority, and be able to advise the horse industry based on sound scientific information.

While Powell said the cause of the problem needs to be identified and proven scientifically, the panel at Keeneland projected a confident front that at least one of the major contributors to the early fetal loss and late-term abortions seen in Kentucky this spring were due to cyanide (see related articles at http://health.bloodhorse.com/).

"We've been accumulating valuable information, including negative information to help eliminate a number of hypotheses," said Powell.

Thursday also was the first time since late April that the Kentucky Livestock Disease Diagnostic Center didn't receive any fetuses or foals attributed to the spring syndromes.

Dr. Lenn Harrison, head of the Diagnostic Center, said to date 9,484 tests, assays, and procedures have been done on samples brought into the center. He continues to report a consistent pattern of lesions in the lungs of late-term foals. He also said researchers identified previously unrecognized lesions along the umbilical cord and amniotic sac. Harrison said many foals had fluid in their lungs and had sucked in material so they might have been gasping or struggling in utero.

Early in the testing process, researchers did not find any cyanide in the Eastern tent caterpillars now viewed at least as a possible culprit in spreading the cyanide from black cherry trees. Harrison said researchers later learned that caterpillars pass material through their digestive tracts within six hours or less, so they needed to be tested quickly after they were captured. After realizing this testing oversight, more caterpillars were tested and found to be strongly positive for cyanide.

The toxicology lab at the University of Illinois assisted the Kentucky Diagnostic Center in looking at tissue samples for cyanide. Included in the tested samples were heart muscle, blood, liver, and kidney.

Heart samples from three different fetuses sent for testing showed low levels of cyanide or cyanide-containing compounds. More samples will be sent for testing to Illinois and other laboratories.

"I'm concerned we only might find cyanide in a small number of samples because it is so elusive," said Harrison. Cyanide is extremely hard to detect after causing an initial insult.

When asked if cyanide was the answer, Harrison returned to his scientific roots and said that all of the results are a roadmap, but the signs point strongly to cyanide being involved. "A number of us are comfortable with this diagnosis," he added.

From the field, Dr. Doug Byars of Haygard-Davidson-McGee veterinary firm reported on various aspects of what veterinarians have seen and are seeing. Byars said one new pericarditis case was seen in the field yesterday (May 23), and that the "bell curve" of incidence of that problem had dropped significantly from the peak last week. He said uveitis (eye)problems also seem to be trailing off.

There aren't many mares left to foal, which reduces the chance of a mare losing a late-term pregnancy from the residual effects of the initial insult of cyanide. Reproductive vets in the field with the Haygard's group are "inconsistent" in what they are finding.

Some are seeing no more early fetal losses, and others see four or five previously pregnant mares becoming "empty" at a time.

Dr. Tom Riddle, a founding partner of Rood and Riddle Equine Hospital, said there still are more questions than answers. He offered statistics from his own mare records through today's exams. He even followed up on mares which had been moved out of state and were pregnant when they left. He said while he knows not all cases of early fetal loss are associated with the current syndrome, he included every mare in his care.According to his information:

Mares bred in February had 40% abortions, which is 5-10% above normal. About 30% of those mares had abnormal alantoic (placental) fluid. He translated that to mean up to 80% of the pregnancies had been affected by mare reproductive loss syndrome.

Mares bred in March had 33% abortions, and 6% abnormal placental fluids. That translated into 39% of pregnancies affected. He said mares bred in April were not far enough along in their pregnancies be included in these figures. Mares shipped out of state followed a similar pattern. He found that in Week 1 of the syndrome encompassing May 4-10, a total of 39% of mares had aborted. By Week 2, May 11-17, 17% of mares had aborted. By Week 3, May 18-24, 8% had aborted.

Riddle said that some pregnancies were compromised with particles in the allantoic fluid and changes in the borders of the placental membranes. "Some aborted after one or two weeks, but some are keeping live foals," he reported. "I don't know if they will continue to survive. I question the quality of foals produced under these circumstances."